A gimbal for a gimbaled mirror optical sensor system includes a mirror support rotatable about a first axis along which an optical sensor suite lies, the first axis being spaced apart from a desired pivot point of a variable line of sight, which may be for example a fixed-size window in the outer wall of an aircraft. The gimbal further includes two generally planar mirrors supported by and rotatable with the mirror support. A first mirror is spaced apart from the optical sensor suite along the first axis and is non-orthogonal to the first axis so as to reflect light from a second axis to the optical sensor suite, wherein the second axis sweeps an arcuate path about the first axis upon rotation of the mirror support. A second mirror lies along the second axis so as to follow the arcuate path upon rotation of the mirror support. The second mirror is pivotable so as to reflect light from the variable line of sight to the first mirror along the second axis. A motion control subsystem controls the rotation of the mirror support and the pivoting of the second mirror such that the variable line of sight pivots about the desired pivot point.